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Is There a Role for Glutaredoxins and BOLAs in the Perception of the Cellular Iron Status in Plants? Pascal Rey, Maël Taupin-Broggini, Jérémy Couturier, Florence Vignols, Nicolas Rouhier

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Pascal Rey, Maël Taupin-Broggini, Jérémy Couturier, Florence Vignols, Nicolas Rouhier. Is There a Role for Glutaredoxins and BOLAs in the Perception of the Cellular Iron Status in Plants?. Frontiers in Plant Science, Frontiers, 2019, 10, pp.712. 10.3389/fpls.2019.00712. hal-02571980v2

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PERSPECTIVE published: 04 June 2019 doi: 10.3389/fpls.2019.00712

Is There a Role for Glutaredoxins and BOLAs in the Perception of the Cellular Iron Status in Plants?

Pascal Rey1, Maël Taupin-Broggini2, Jérémy Couturier3, Florence Vignols2 and Nicolas Rouhier3*

1 Plant Protective Proteins Team, CEA, CNRS, BIAM, Aix-Marseille University, Saint-Paul-lez-Durance, France, 2 Biochimie et Physiologie Moléculaire des Plantes, CNRS/INRA/Université de Montpellier/SupAgro, Montpellier, France, 3 Université de Lorraine, INRA, IAM, Nancy, France

Glutaredoxins (GRXs) have at least three major identiﬁed functions. In apoforms,

Edited by: they exhibit oxidoreductase activity controlling notably protein glutathionylation/ Thomas J. Buckhout, deglutathionylation. In holoforms, i.e., iron–sulfur (Fe–S) cluster-bridging forms, they Humboldt University of Berlin, act as maturation factors for the biogenesis of Fe–S proteins or as regulators of iron Germany homeostasis contributing directly or indirectly to the sensing of cellular iron status and/or Reviewed by: Qingyu Wu, distribution. The latter functions seem intimately connected with the capacity of speciﬁc Institute of Agricultural Resources GRXs to form [2Fe–2S] cluster-bridging homodimeric or heterodimeric complexes with and Regional Planning (CAAS), China Ping Lan, BOLA proteins. In yeast species, both proteins modulate the localization and/or activity Institute of Soil Science (CAS), China of transcription factors regulating genes coding for proteins involved in iron uptake and *Correspondence: intracellular sequestration in response notably to iron deﬁciency. Whereas vertebrate Nicolas Rouhier GRX and BOLA isoforms may display similar functions, the involved partner proteins are [email protected] different. We perform here a critical evaluation of the results supporting the implication Specialty section: of both protein families in similar signaling pathways in plants and provide ideas and This article was submitted to experimental strategies to delineate further their functions. Plant Nutrition, a section of the journal Keywords: BOLA, glutaredoxins, iron–sulfur center, maturation factor, iron homeostasis Frontiers in Plant Science Received: 05 March 2019 Accepted: 14 May 2019 INTRODUCTION Published: 04 June 2019 Citation: Many cellular reactions and biological processes require metalloproteins, among which those Rey P, Taupin-Broggini M, containing iron (Fe) cofactors such as mononuclear and dinuclear (non-heme) Fe centers, hemes Couturier J, Vignols F and Rouhier N and iron–sulfur (Fe–S) clusters, are particularly crucial. Unlike other metals such as copper or zinc, (2019) Is There a Role there is no universal Fe chaperone described and so far, only poly rC-binding proteins (PCBPs) were for Glutaredoxins and BOLAs in the Perception of the Cellular Iron shown to coordinate Fe entry in the cytosol and serve for the metalation of non-heme Fe enzymes Status in Plants? in mammals (Philpott et al., 2017). In contrast, the synthesis/assembly of hemes and Fe–S clusters Front. Plant Sci. 10:712. requires more complex and universally conserved pathways (Couturier et al., 2013; Barupala et al., doi: 10.3389/fpls.2019.00712 2016). The machineries dedicated to the maturation of Fe–S proteins present in mitochondria

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and chloroplasts, named ISC (iron–sulfur cluster) and SUF in the β1–β2 loop, referred to as [H/C] loop (Figure 1A; (sulfur mobilization), respectively, are also found in bacteria Li et al., 2011, 2012; Roret et al., 2014; Dlouhy et al., 2016; (Lill, 2009). On the other hand, cytosolic and nuclear Fe–S Nasta et al., 2017). proteins are maturated via the eukaryote-specific cytosolic iron– Hereafter, based on the most recent results and known roles sulfur cluster assembly (CIA) machinery, which is, however, in non-photosynthetic organisms, we discuss the putative or dependent on the mitochondrial ISC machinery for sulfur supply confirmed functions of GRX and BOLA, alone or in complex, in (Lill, 2009). Hence, given the high cellular demand for iron, photosynthetic organisms. sophisticated systems exist to control Fe uptake and intracellular distribution due to its potential toxicity. Strikingly, the Fe sensing systems and associated transcription factors generally differ in THE CLASS II GRX AND BOLA COUPLE bacteria, yeast/fungi, mammals, and plants, but might include PROTEINS PRESENT IN BACTERIA OR common actors such as glutaredoxins (GRXs) and BOLAs (Couturier et al., 2015). IN EUKARYOTE ORGANELLES ARE Two GRX classes, I and II, are present in most INVOLVED IN THE SYNTHESIS OF FE–S organisms whereas additional classes are specific to some CLUSTERS species/genus/kingdoms (Alves et al., 2009; Couturier et al., 2009). GRXs of the first class are involved in redox regulation, The first evidence about GRX involvement in the biogenesis of reducing protein disulfides or glutathione-protein mixed Fe–S proteins were obtained from a S. cerevisiae mutant for disulfides. GRXs from class II participate in the regulation the mitochondrial Grx5 (Table 1; Rodríguez-Manzaneque et al., of Fe homeostasis (Mühlenhoff et al., 2010; Haunhorst et al., 2002; Mühlenhoff et al., 2003). Orthologs of this single domain- 2013) and in the maturation of Fe–S proteins owing to containing GRX are found in bacteria, archaea and plant plastids. their capacity to ligate and exchange [2Fe–2S] clusters with The current view is that Grx5 is required for the maturation partner proteins (Table 1; Rodríguez-Manzaneque et al., 2002; of all types of Fe–S clusters in mitochondria, receiving a [2Fe– Bandyopadhyay et al., 2008). They are also referred to as 2S] cluster from ISCU-type scaffold proteins and transferring monothiol GRXs or CGFS GRXs owing to their conserved CGFS it to ISCA-type transfer proteins for subsequent maturation of active site signature. [4Fe–4S] proteins (Figure 1B). Grx5 is also required for the Regarding the BOLA family, an extensive phylogenetic maturation of nucleo-cytosolic Fe–S proteins and the activation analysis allowed delineating four groups, namely BOLA1– of the Aft1 transcription factor, pointing to its key position in BOLA4 (Couturier et al., 2014). BOLA1s are present in S. cerevisiae (see below) (Uzarska et al., 2013). Yeast Bol1 and both bacteria and eukaryotes, BOLA2s and BOLA3s in Bol3, which have the capacity to form heterodimers with Grx5, eukaryotes and BOLA4s in photosynthetic organisms, archaea, were later shown to be required for a specific set of mitochondrial and bacteria. Pioneer works revealed functions for Escherichia [4Fe–4S] proteins, without affecting de novo synthesis of [2Fe– coli BolA in the regulation of cell morphology, possibly as a 2S] proteins (Uzarska et al., 2016). So far, human BOLA3, transcriptional regulator (Aldea et al., 1989), for Saccharomyces but not BOLA1, has been demonstrated as required for the cerevisiae cytosolic Bol2/Fra2 (Fe repressor of activation 2) maturation of specific Fe–S proteins (Table 1; Cameron et al., in the regulation of iron homeostasis (Lesuisse et al., 2005; 2011; Willems et al., 2013). The client proteins are notably Kumánovics et al., 2008), and for mitochondrial BOLAs (human the succinate dehydrogenase/complex II and lipoate synthase. BOLA3 and yeast Bol1, Bol3) in the maturation of Fe–S Moreover, the fact that bol1–bol31 mutants are neither affected clusters (Table 1; Cameron et al., 2011; Melber et al., 2016; in the CIA machinery, nor in Aft1 activation, indicates that Grx5 Uzarska et al., 2016). has physiological roles independent of Bol1 and Bol3 (Uzarska A very close relationship between class II GRXs and et al., 2016). Additional studies suggested that Bol1 indeed BOLAs was initially evident from genome (gene co-occurrence acts early in the ISC pathway in concert with Grx5 (possibly and clustering, existence of fusion proteins) and large-scale only for [4Fe–4S] proteins) whereas Bol3 may preferentially act interactomic analyses in various organisms (reviewed in with NFU1, a late Fe–S cluster transfer protein, to preserve Przybyla-Toscano et al., 2017). Then, the molecular and the [4Fe–4S] center found in some specific mitochondrial client structural determinants of the complexes were investigated in proteins, as lipoate synthase, from oxidative damage (Figure 1B; detail using mutational, spectroscopic and structural analyses Melber et al., 2016). on recombinant proteins. This led to demonstrate that class Concerning bacteria, the sole Grx isoform (Grx4/D) and II GRXs and BOLAs form both apo- and holo-heterodimers both BolAs (BolA and IbaG) from E. coli were recently shown bridging a [2Fe–2S] cluster, usually more stable than the [2Fe– as implicated in the maturation of the respiratory complexes 2S] cluster-bridging GRX homodimers, and to identify the I and II, but the effects are only visible when multiple genes residues serving as ligands (Li and Outten, 2012; Couturier are mutated (Burschel et al., 2019). This role in maturating et al., 2015; Przybyla-Toscano et al., 2017). In GRX-BOLA holo- Fe–S proteins is consistent with (i) the synthetic lethality heterodimers, the [2Fe–2S] cluster is ligated using the GRX of the Grx4 gene with genes present in the ISC operon conserved cysteine, a cysteine from glutathione (as in GRX holo- (Butland et al., 2008), (ii) the interaction in vitro of Grx4 homodimers), and, on the BOLA side, using a C-terminally with the MiaB Fe–S protein (Boutigny et al., 2013), and located conserved histidine and an histidine or a cysteine (iii) the capacity of Grx4-BolA and Grx4-IbaG to form the

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TABLE 1 | Iron-related phenotypes of bolA and glutaredoxin mutants from various sources.

Organism Protein names Mutant phenotype(s) References

Mono-domain Saccharomyces Grx5 Defaults in Fe–S cluster assembly Rodríguez-Manzaneque et al., (organellar) GRXs cerevisiae 2002; Mühlenhoff et al., 2003 Schizosaccharomyces Grx5 Defaults in Fe–S cluster assembly, decreased amount Chung et al., 2005; Kim et al., 2010 pombe of mitochondrial DNA, reduced growth, and sensitivity toward oxidants Danio rerio GRX5 Embryo lethal Wingert et al., 2005 Homo sapiens GLRX5 Defaults in Fe–S cluster assembly leading to Camaschella et al., 2007; Ye et al., sideroblastic anemia 2010 Trypanosoma brucei 1-C-Grx1 Lethal Comini et al., 2008 Sinorhizobium meliloti Grx2 Defaults in Fe–S cluster assembly, deregulation of RirA Benyamina et al., 2013 transcriptional activity, increased intracellular iron content, modiﬁed nodule development Escherichia coli Grx4 Sensitivity to iron depletion, defect in respiratory Yeung et al., 2011; Burschel et al., complex I 2019 Arabidopsis thaliana GRXS14 Sensitivity to prolonged darkness Rey et al., 2017 Arabidopsis thaliana GRXS15 Lethal, decreased amounts of lipoate synthase and of Moseler et al., 2015; Ströher et al., lipoic acid dependent H subunits of the glycine 2016 cleavage system in RNAi lines Arabidopsis thaliana GRXS16 None described for co-suppressed and RNAi lines Rey et al., 2017 Multi-domain Saccharomyces Grx3 Impaired regulation of Aft1/2 and iron homeostasis Ojeda et al., 2006; Pujol-Carrion (cytosolic) GRXs cerevisiae et al., 2006 Saccharomyces Grx4 Impaired regulation of Aft1/2 and iron homeostasis Ojeda et al., 2006; Pujol-Carrion cerevisiae et al., 2006 Saccharomyces Grx3–Grx4 Lethal in some background. Impaired iron trafﬁcking Pujol-Carrion et al., 2006; cerevisiae and assembly of Fe–S proteins, heme, and Mühlenhoff et al., 2010 iron-containing proteins Schizosaccharomyces Grx4 Lethal Chung et al., 2005 pombe Cryptococcus Grx4 Slow growth upon iron deprivation Attarian et al., 2018 neoformans Danio rerio GRX3 Impaired heme synthesis and Fe–S protein maturation Haunhorst et al., 2013 Homo sapiens GLRX3/PICOT Decreased activities of cytosolic Fe–S proteins Haunhorst et al., 2013 Arabidopsis thaliana GRXS17 Growth defects (meristem arrest) upon elevated Cheng et al., 2011; Knuesting temperature and long photoperiod. No decrease in et al., 2015; Yu et al., 2017 cytosolic Fe–S protein activity BOLA Saccharomyces Bol1 No growth defect and no decrease in Fe–S enzyme Melber et al., 2016; Uzarska et al., cerevisiae activity 2016 Saccharomyces Bol3 Slightly decreased complex II (SDH) activity Melber et al., 2016; Uzarska et al., cerevisiae 2016 Saccharomyces Bol1–Bol3 Decreased activity of lipoic acid-dependent enzymes, Melber et al., 2016; Uzarska et al., cerevisiae aconitase, and respiratory complex II 2016 Saccharomyces Bol2/Fra2 Impaired regulation of Aft1/2 and iron homeostasis Kumánovics et al., 2008; Uzarska cerevisiae et al., 2016 Schizosaccharomyces BolA2/ Fra2 Impaired regulation of the Fep1 transcription factor Jacques et al., 2014 pombe Homo sapiens BOLA1 Oxidation of the mitochondrial GSH pool Willems et al., 2013 Homo sapiens BOLA2 None described for siRNA lines Frey et al., 2016 Homo sapiens BOLA3 Defect in lipoic acid-dependent enzymes and in Cameron et al., 2011 respiratory complexes I and II Escherichia coli BolA Partial defect in respiratory complex I assembly Burschel et al., 2019 Escherichia coli IbaG None described Burschel et al., 2019 Escherichia coli BolA – IbaG Decreased complex II activity Burschel et al., 2019 Salmonella typhimurium BolA Decreased resistance to acidic and oxidative stresses Mil-Homens et al., 2018 and decreased virulence Arabidopsis thaliana BOLA2 None described under control conditions, increased Qin et al., 2015 resistance to oxidative conditions

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FIGURE 1 | Continued

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FIGURE 1 | Properties and hypothetical roles of the class II GRX-BOLA couple in plants. (A) Tridimensional structures of plastidial Arabidopsis thaliana BOLA1 and GRXS14 proteins highlighting the residues involved in the interactions. On the top, superimposition of AtBOLA1 (green) and AtBOLA2 (blue) structures. Both proteins have a α/β-structure made of four helices and three strands with an α1β1β2η2α3β3α4 (η: 310-helix) topology (Roret et al., 2014). The β-strands form a central three-stranded β-sheet. In addition to the extended C-terminal part in AtBOLA2, both proteins differ by the length of the β1–β2 loop (in red in BOLA1), referred to as [H/C] loop, and which contains the histidine (His97 in AtBOLA1) or cysteine (Cys29 in AtBOLA2) residues provided by BOLA proteins for Fe–S cluster bridging together with the His66 (AtBOLA2) or His144 (AtBOLA1). The putative DNA binding site in BOLAs is formed by the η2 and α3 helices, the loop containing a specific FXGX signature (type II β-turn), the α3 helix containing a positively charged RHR motif and the β3 strand. Below, from left to right, AtBOLA2 structure showing 18 residues (mainly part of the β2 and β3 strands and α3 helix) identified by NMR titration as involved in the interaction with apo-AtGRXS14; and AtGRXS14 structure showing 32 residues (many present in the C-terminal α3 and α4 helices) identified by NMR titration as involved in the interaction with AtBOLA2 (Roret et al., 2014). These residues, plus some additional ones, are also involved in the formation of the [2Fe–2S] cluster-bridged heterodimer as determined using human proteins (Nasta et al., 2017). (B) Hypothetical model for the role of GRXS15 and BOLA4 in plant mitochondria. By analogy with the yeast system, GRXS15 (shortened as GRX) should receive a [2Fe–2S] cluster synthesized de novo by a multi-protein assembly complex (details about the proteins involved in the early steps of Fe–S cluster assembly and transfer have been omitted). GRXS15 is supposed to transfer its [2Fe–2S] cluster to client proteins as the mitochondrial ferredoxin 1 (mFDX1) (Moseler et al., 2015) or to ISCA proteins for the reductive conversion of two [2Fe–2S] clusters into a [4Fe–4S] cluster (as shown with human proteins) and its subsequent delivery to client proteins bearing such cluster. In the absence of genetic analysis about bola4 mutants, the contribution of BOLA4 (shortened as BOLA) for the respective roles of GRXS15 is unclear, but the confirmed interaction between both proteins (Couturier et al., 2014) prompted us to include BOLA at this step as yeast Bol1/3 proteins are only required for the maturation of [4Fe–4S] proteins. The specific defects observed for aconitase (ACO) and lipoic-acid dependent proteins in the GRXS15 mutant lines indicate a direct or indirect role for GRXS15 in the maturation of both lipoate synthase (LIP1) and aconitase. Finally, whether GRXS15 is required for the maturation and activity of cytosolic and nuclear Fe–S proteins by fueling the CIA machinery as shown for yeast Grx5, or by indirectly contributing to the synthesis of molybdenum cofactor, that is present in several cytosolic Fe–S proteins, is unknown. (C) Roles associated with the various oligomeric forms involving nucleo-cytosolic GRXs and BOLAs irrespective of the organisms considered. The color code is as follows: in blue, functions associated with apo-dimeric GRX forms, in purple those associated with apo-BOLA and in black those associated with the GRX homodimeric or GRX-BOLA heterodimeric forms bridging a [2Fe–2S] cluster.

usual [2Fe–2S] cluster-bridging heterodimers (Yeung et al., 2011; determinants (Bandyopadhyay et al., 2008; Moseler et al., 2015; Dlouhy et al., 2016). In Sinorhizobium meliloti, deletion of Uzarska et al., 2018). the sole class II GRX also leads to impaired maturation of Fe–S proteins and increased intracellular iron content (Benyamina et al., 2013). MULTIPLE FUNCTIONS IN THE In plants, the corresponding mitochondrial GRX is named REGULATION OF IRON HOMEOSTASIS GRXS15. Knockout Arabidopsis mutants are lethal due to defective embryo development (Moseler et al., 2015). Plants OF THE CLASS II GRX AND BOLA expressing a mutated GRXS15 form modified for its ability to COUPLE IN THE CYTOSOL/NUCLEUS coordinate an Fe–S cluster exhibit severely reduced growth and OF EUKARYOTES impaired aconitase activity (Moseler et al., 2015). Additionally, Arabidopsis GRXS15 down-regulated lines display slowed Eukaryote cytosolic class II GRXs are multidomain proteins growth and impaired activity of enzymes dependent on formed by an N-terminal thioredoxin-like domain fused to lipoic acid, the synthesis of which is ensured by the Fe– one to three GRX domains (Couturier et al., 2009). Most S cluster-containing lipoyl synthase (Ströher et al., 2016). organisms have a single GRX of this type and also a single Whether GRXS15 fulfills its function in concert with BOLA4, cytosolic BOLA isoform, referred to as BOLA2/Bol2/Fra2. the sole mitochondrial BOLA, remains to be explored, but The pioneering studies showing the involvement of class II their interaction was demonstrated in yeast and in planta GRXs and BOLAs in Fe homeostasis have been conducted in (Figure 1B; Couturier et al., 2014). Plants also have class S. cerevisiae mutants deregulated in Grx3, Grx4, and Bol2/Fra2 II GRXs (GRXS14 and S16) and mono-domain BOLAs genes (Table 1; Lesuisse et al., 2005; Ojeda et al., 2006; (BOLA1, BOLA4) in plastids (Couturier et al., 2013). So far, Pujol-Carrion et al., 2006). In yeast, the regulation of Fe in planta evidence for their implication in the biogenesis concentration is achieved at the transcriptional level by low- of Fe–S proteins are scarce (Table 1). GRXS14-deficient (Aft1 and Aft2) and high-level (Yap5) sensing transcription Arabidopsis plants exhibit accelerated chlorophyll loss upon factors and at the post-transcriptional level by mRNA-binding prolonged darkness, a treatment also leading to a decreased proteins (Outten and Albetel, 2013). Both types of transcription abundance of proteins acting in Fe–S cluster metabolism factors bind [2Fe–2S] clusters allowing them to perceive the (Rey et al., 2017). Nevertheless, the demonstration that cellular Fe or Fe–S cluster status (Poor et al., 2014; Rietzschel Arabidopsis and/or poplar GRXS14 and GRXS16 interact et al., 2015). Whereas Grx4 expression is regulated by Yap5, both with BOLA1 and BOLA4 (Couturier et al., 2014), it is not documented whether Yap5 localization or activity is bind Fe–S clusters alone or in complex (Bandyopadhyay controlled by a GRX/BOLA complex. Regarding Aft1/Aft2, their et al., 2008; Dhalleine et al., 2014; Roret et al., 2014) and subcellular (nuclear vs. cytosolic) localization is controlled by transfer it to partner proteins (Mapolelo et al., 2013) give a Fra2-Grx3/4 inhibitory complex (possibly requiring also the strong credence to such a role. Even more importantly, all aminopeptidase Fra1) (Kumánovics et al., 2008). The current plant GRX and BOLA genes complement totally or partially view is that the presence of an Fe–S cluster in the Fra2- (GRXS15) the corresponding yeast grx5 and bol1–bol3 mutants, Grx3/4 complex is synonymous of iron-replete conditions and indicating that they possess similar structural and functional of a correct functioning of the ISC machinery (Figure 1C;

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Kumánovics et al., 2008). By transferring a cluster to Aft1/2, the GLRX3 homodimers and GLRX3-BOLA2 trimeric complexes GRX-BOLA complex should either retain them in the cytosol bridging two [2Fe–2S] clusters can deliver their clusters to the or promote their dissociation from DNA if in the nucleus (Ueta anamorsin/CIAPIN/DRE2 protein (Banci et al., 2015a,b). From et al., 2012; Poor et al., 2014). the observation that the maturation of yeast Grx3/4 and human Some aspects of Fe homeostasis in other yeasts and fungi GLRX3-BOLA2 heterodimers requires the mitochondrial ISC are also controlled by GRX and/or BOLA. In Cryptococcus machinery but not CIA components (Mühlenhoff et al., 2010; neoformans, Fe repletion promotes Grx4 relocation from Frey et al., 2016), it is concluded that cytosolic class II the nucleus to the cytoplasm allowing the regulation of GRXs should build their cluster from a sulfur compound Cir1, a master regulator of Fe-responsive genes (Attarian exported by the mitochondrial ATM transporter (Figure 1C). et al., 2018). In Schizosaccharomyces pombe, Fe metabolism In yeast grx3/41, the Fe or Fe-cofactor insertion in various is regulated by two transcriptional repressors, the GATA-type proteins present in cytosol [catalase, ribonucleotide reductase iron sensing Fep1 and the CCAAT-binding factor complex (RNR)], and mitochondria (complexes II and III, aconitase, subunit Php4 (Brault et al., 2015). Their localization and/or Coq7 mono-oxygenase) is altered (Mühlenhoff et al., 2010; DNA binding activity are regulated by Grx4 and/or Fra2 Zhang et al., 2011). Moreover, the respective increased and (reviewed in Outten and Albetel, 2013; Brault et al., 2015). decreased Fe levels in cytosol and mitochondria of Grx3/4 The binding of a [2Fe–2S] cluster between Grx4 and Php4 depleted cells pointed to impaired Fe distribution (Mühlenhoff may promote Php4 release from the CCAAT-binding complex et al., 2010). These additional functions of yeast Grx3/4 at the DNA targets and suppress its inhibitory effect on the are well exemplified in the case of RNR di-iron cofactor expression of Fe storage genes (Dlouhy et al., 2017). Unlike biogenesis because Grx4 provides the Fe atoms, but also Php4, the regulation of which does not involve Fra2, the serves for the maturation of holo-Dre2, that provides the formation of a [2Fe–2S]-Grx4/Fra2 heterodimeric complex is required electrons (Li et al., 2017). A contribution of yeast required for regulating Fep1 activation (Jacques et al., 2014; Bol2 for these functions is unclear even though a general Encinar del Dedo et al., 2015). role in cytosolic Fe–S protein maturation is excluded (Uzarska In mammals, the regulation of Fe metabolism and homeostasis et al., 2016). In human, GLRX3-BOLA2 trimeric complexes is ensured by IRP1/2 and RNA-binding proteins (Rouault bridging two [2Fe–2S] clusters were proposed to constitute and Maio, 2017). Under Fe limitation, both IRPs bind to a reservoir for delivering Fe or Fe–S cluster to some Fe- the so-called Iron Responsive Elements (IREs) in untranslated containing target proteins based notably on the six–eightfold regions of mRNAs coding for proteins implicated in Fe increased abundance observed in response to elevated iron assimilation and homeostasis (Rouault and Maio, 2017). Doing (Frey et al., 2016). so, they control either mRNA stabilization or translational The function of GRXS17, the sole nucleo-cytosolic class II blocking. Whereas IRP2 release from IREs is mediated by GRX in plants, has been explored using several approaches. proteasomal degradation (Guo et al., 1995), IRP1 function Tandem affinity purification using a tagged GRX form expressed may depend on GLRX3/PICOT (but also on mitochondrial in Arabidopsis cell cultures and seedlings pointed to the GLRX5) as it relies on the binding of an Fe–S cluster. Under association of GRXS17 with CIA components and BOLA2 (Iñigo Fe sufficiency, IRP1 binds a [4Fe–4S] cluster and acts as an et al., 2016). The interactions with DRE2 and BOLA2 have aconitase whereas under Fe limitation the protein turns into been confirmed in vivo by binary yeast two-hybrid and BiFC an apoform binding to IREs. Consequently, IRP1 requires and/or in vitro by co-expression in E. coli (Couturier et al., 2014; functional mitochondrial and cytosolic Fe–S cluster assembly Dhalleine et al., 2014; Iñigo et al., 2016). As GRXs interact with machineries. Having two GRX domains, human GLRX3 forms Dre2/Anamorsin in yeast and human cells (Zhang et al., 2011; homodimers or heterotrimers with two BOLA2 molecules Banci et al., 2015b), the only direct CIA partner of GRXS17 bridging two [2Fe–2S] clusters (Li et al., 2012; Banci et al., might be DRE2 and the other proteins part of a complex. 2015b; Frey et al., 2016). It also binds a [4Fe–4S] cluster Besides, the binding of GRXS17 with putative Fe–S client proteins and transfers it in vitro to an apo-IRP1 (Xia et al., 2015). involved in purine salvage (xanthine dehydrogenase 1) or tRNA GLRX3 silencing in human HELA cells decreases the activity modification (thiouridylase subunits 1 and 2) was shown (Iñigo of several cytosolic Fe–S proteins, including IRP1 (Table 1; et al., 2016). Thus, one would expect that plants deficient Haunhorst et al., 2013). In zebrafish, GLRX3 deletion impairs in GRXS17 display a marked phenotype in relation with Fe heme biosynthesis during embryo development (Haunhorst et al., metabolism, but the analysis of Arabidopsis grxs17 plants led to 2013). All of this indicates important functions of vertebrate relatively complex data. Indeed, their development is only mildly GLRX3 in Fe metabolism. affected under standard growth conditions, but gets severely In addition to an Fe sensing function, an Fe or Fe–S cluster impaired (elongated leaves, modified shoot apical meristem trafficking function was proposed for yeast Grx3/4 and the structure, and altered auxin response) at high temperature or human GLRX3-BOLA2 complex to ensure proper assembly of under long photoperiod (Cheng et al., 2011; Knuesting et al., several types of Fe-containing centers. In fact, most multidomain 2015). It is not yet clear whether a redox- and/or an Fe- GRXs are able to rescue the Fe–S cluster maturation defects related function of GRXS17 is responsible for these alterations. of the yeast grx5 mutant (Molina et al., 2004; Bandyopadhyay In fact, in vitro pull-downs performed using the recombinant et al., 2008; Knuesting et al., 2015) suggesting that they have the protein allowed recovering many non-Fe–S proteins including capacity of exchanging Fe–S clusters. Accordingly, both human the NF-YC11 transcriptional regulator (Knuesting et al., 2015).

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Moreover, there is no variation in the Fe content in mature types of Fe cofactors (including heme and non-heme Fe centers) leaves and only a slight increase in seeds (Yu et al., 2017) and/or to serve for Dre2 maturation, thus contributing to of grxs17 plants that exhibit no or minor decreases in the the correct functioning of the CIA machinery. In this case, activity of three Fe–S containing enzymes: aconitase, aldehyde Grx3/4 have an exclusive or predominant role because the oxidase and xanthine dehydrogenase (Knuesting et al., 2015; corresponding mutant is lethal or strongly affected, unlike Iñigo et al., 2016). On the other hand, GRXS17-deficient the bol2/fra2 mutant. Experimental evidence indicate that the lines exhibit a slightly increased sensitivity to genotoxic stress involvement of GRX and/or BOLA in DRE2 maturation is likely which is reminiscent of mutants compromised in the CIA also true in mammals and plants, but evidence supporting other pathway (Iñigo et al., 2016). Finally, when GRXS17-deficient functions are scarce. lines are exposed to Fe deficiency, the primary root growth A first prerequisite to future molecular and physiological reduction, that is already visible under standard conditions, is analyses is to generate the missing single knock-out lines but exacerbated and ROS levels are elevated (Iñigo et al., 2016; also multiple knock-out lines for possibly redundant proteins. Yu et al., 2017). Whether plant GRXS17 and BOLA2 act in This would be particularly important to obtain lines combining concert remains unclear. The Arabidopsis bola2 (incorrectly mutations for GRXS14 and GRXS16, for BOLA1 and BOLA4, named bola3) mutant displays no phenotype under control but also for GRXS17 and the only other Fe–S ligating GRXs conditions and no change in the activity of typical Fe–S reported so far in the cytosol, namely GRXC1 (Rouhier et al., enzymes (Qin et al., 2015). Surprisingly, this line is more 2007), or BOLA2. In case the single or multiple mutants tolerant to oxidative stress generated by an Fe excess (Qin are lethal, an option for obtaining viable lines would be to et al., 2015). In conclusion, bola2 and grxs17 plants exhibit generate RNAi lines as for GRXS15, but also dominant negative relatively mild phenotypes, visible mostly under stress conditions, mutant lines expressing mutated versions of GRX or BOLA compared to those described for human and yeast orthologs unable for instance to ligate the Fe–S cluster, i.e., mutated and to the embryo-lethality of most Arabidopsis mutants for the catalytic cysteine of GRXs or the conserved histidine defective for early acting CIA components (Bernard et al., residue of BOLA. 2013). This raises some questions about the exact functions At the physiological level, the growth of these plants of BOLA2 and GRXS17 in the regulation of Fe homeostasis should be analyzed under standard conditions, but also in plant cells and about the existence of an alternative under environmental constraints as the shoot phenotypes of system, notably for delivering Fe–S clusters to DRE2, whose grxs17 mutants are only visible in specific conditions. For function is essential. the BOLA2-GRXS17 couple, understanding their connection and discriminating between Fe- or redox-related functions will require in particular to assess the phenotypes of the ROADMAP TOWARD THE corresponding mutants in the same experimental setup and UNDERSTANDING OF THE ROLES OF conditions. Considering the described importance of GSH GRX/BOLA COUPLES IN PLANTS for ligating Fe–S cluster in GRX homodimer or GRX- BOLA heterodimer and for the maturation of cytosolic Fe–S In this section, we propose some ideas and experimental proteins (Sipos et al., 2002), crossing some of these mutants strategies that should warrant deciphering the functions with mutants having an altered GSH homeostasis would associated to GRX/BOLA couples in plants. certainly be informative. Evidence obtained so far indicate that the class II mono- In other respects, an obvious strategy is to measure the domain GRXs and BOLAs present in mitochondria of non- abundance/activity of representative Fe–S proteins in these lines. plant eukaryotes and in bacteria act as maturation factors However, performing quantitative proteomic and metabolomic for the biogenesis of Fe–S proteins. A similar role seems approaches may be more informative and help obtaining a true for the plant mitochondrial GRXS15, but it is now broader view of the molecular and cellular mechanisms affected mandatory to examine whether it also contributes to the and of the compensations established. It may also rapidly point maturation of extra-mitochondrial proteins. Another challenge to metabolic differences existing among mutants. will be to understand why it is essential in plants unlike in In all cases, determining the identity of the direct and indirect yeast. Also, the physiological consequences of BOLA4 depletion targets of both GRXs and BOLAs would represent a mandatory must be investigated to see whether this fits with a function information. For instance, the proteins involved in the Fe–S connected to GRXS15. Concerning plastidial proteins (GRXS14, cluster maturation process may act at different steps. Various GRXS16, BOLA1, and BOLA4), a role in the maturation approaches complementary to quantitative proteomics proved of Fe–S proteins still needs to be demonstrated in planta, valuable even for detecting supposedly transient interactions despite they can functionally substitute to their mitochondrial among Fe–S cluster donors and acceptors (Touraine et al., 2019). yeast counterparts. Hence, it is possible to combine it to another non-targeted With regard to the cytosolic multi-domain GRXs and BOLAs, approach such as co-immunoprecipitation or to binary yeast two- a role in Fe metabolism seems evolutionary conserved, but their hybrid experiments which has the advantage for instance to allow contribution and partners differ. In yeast, their primary function studying rapidly sequence requirements by mutational analysis. is to regulate Fe-responsive transcription factors. Additional In summary, the combination of genetic approaches, functions are to ensure a proper Fe distribution toward all omics analyses and conventional biochemical tools should

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in principle allow better delineating the roles and ACKNOWLEDGMENTS speciﬁcities of GRX/BOLA couples in the maintenance of Fe homeostasis in plants. Ms. Anna Moseler is greatly acknowledged for the artwork on Figure 1. DATA AVAILABILITY FUNDING All datasets analyzed for this study are included in the manuscript and the Supplementary Files. The UMR1136 is supported by a grant overseen by the French National Research Agency (ANR) as part of the “Investissements d’Avenir” program (ANR-11- AUTHOR CONTRIBUTIONS LABX-0002-01, Lab of Excellence ARBRE). The work on plant GRX and BOLA proteins was supported All authors wrote the text and approved the ﬁnal version by the Agence Nationale de la Recherche (Grant of the manuscript. No. 2010BLAN1616).

REFERENCES Butland, G., Babu, M., Díaz-Mejía, J. J., Bohdana, F., Phanse, S., Gold, B., et al. (2008). eSGA: E. coli synthetic genetic array analysis. Nat. Methods 5, 789–795. Aldea, M., Garrido, T., Hernández-Chico, C., Vicente, M., and Kushner, S. R. doi: 10.1038/nmeth.1239 (1989). Induction of a growth-phase-dependent promoter triggers transcription Camaschella, C., Campanella, A., De Falco, L., Boschetto, L., Merlini, R., Silvestri, of bolA, an Escherichia coli morphogene. EMBO J. 8, 3923–3931. doi: 10.1002/ L., et al. (2007). The human counterpart of zebrafish shiraz shows sideroblastic- j.1460-2075.1989.tb08573.x like microcytic anemia and iron overload. Blood 110, 1353–1358. doi: 10.1182/ Alves, R., Vilaprinyo, E., Sorribas, A., and Herrero, E. (2009). Evolution based blood-2007-02-072520 on domain combinations: the case of glutaredoxins. BMC Evol. Biol. 9:66. Cameron, J. M., Janer, A., Levandovskiy, V., Mackay, N., Rouault, T. A., Tong, doi: 10.1186/1471-2148-9-66 W.-H., et al. (2011). Mutations in iron-sulfur cluster scaffold genes NFU1 and Attarian, R., Hu, G., Sánchez-León, E., Caza, M., Croll, D., Do, E., et al. (2018). BOLA3 cause a fatal deficiency of multiple respiratory chain and 2-oxoacid The monothiol glutaredoxin grx4 regulates iron homeostasis and virulence in dehydrogenase enzymes. Am. J. Hum. Genet. 89, 486–495. doi: 10.1016/j.ajhg. Cryptococcus neoformans. mBio 9:e02377-18. doi: 10.1128/mBio.02377-18 2011.08.011 Banci, L., Camponeschi, F., Ciofi-Baffoni, S., and Muzzioli, R. (2015a). Elucidating Cheng, N.-H., Liu, J.-Z., Liu, X., Wu, Q., Thompson, S. M., Lin, J., the molecular function of human BOLA2 in GRX3-dependent anamorsin et al. (2011). Arabidopsis monothiol glutaredoxin, AtGRXS17, is critical maturation pathway. J. Am. Chem. Soc. 137, 16133–16143. doi: 10.1021/jacs. for temperature-dependent postembryonic growth and development via 5b10592 modulating auxin response. J. Biol. Chem. 286, 20398–20406. doi: 10.1074/jbc. Banci, L., Ciofi-Baffoni, S., Gajda, K., Muzzioli, R., Peruzzini, R., and Winkelmann, M110.201707 J. (2015b). N-terminal domains mediate [2Fe-2S] cluster transfer from Chung, W.-H., Kim, K.-D., and Roe, J.-H. (2005). Localization and function glutaredoxin-3 to anamorsin. Nat. Chem. Biol. 11, 772–778. doi: 10.1038/ of three monothiol glutaredoxins in Schizosaccharomyces pombe. Biochem. nchembio.1892 Biophys. Res. Commun. 330, 604–610. doi: 10.1016/j.bbrc.2005.02.183 Bandyopadhyay, S., Gama, F., Molina-Navarro, M. M., Gualberto, J. M., Claxton, Comini, M. A., Rettig, J., Dirdjaja, N., Hanschmann, E.-M., Berndt, C., and R., Naik, S. G., et al. (2008). Chloroplast monothiol glutaredoxins as scaffold Krauth-Siegel, R. L. (2008). Monothiol glutaredoxin-1 is an essential iron-sulfur proteins for the assembly and delivery of [2Fe-2S] clusters. EMBO J. 27, protein in the mitochondrion of African trypanosomes. J. Biol. Chem. 283, 1122–1133. doi: 10.1038/emboj.2008.50 27785–27798. doi: 10.1074/jbc.M802010200 Barupala, D. P., Dzul, S. P., Riggs-Gelasco, P. J., and Stemmler, T. L. Couturier, J., Jacquot, J.-P., and Rouhier, N. (2009). Evolution and diversity of (2016). Synthesis, delivery and regulation of eukaryotic heme and Fe-S glutaredoxins in photosynthetic organisms. Cell. Mol. Life Sci. 66, 2539–2557. cluster cofactors. Arch. Biochem. Biophys. 592, 60–75. doi: 10.1016/j.abb.2016. doi: 10.1007/s00018-009-0054-y 01.010 Couturier, J., Przybyla-Toscano, J., Roret, T., Didierjean, C., and Rouhier, N. Benyamina, S. M., Baldacci-Cresp, F., Couturier, J., Chibani, K., Hopkins, J., (2015). The roles of glutaredoxins ligating Fe-S clusters: sensing, transfer Bekki, A., et al. (2013). Two Sinorhizobium meliloti glutaredoxins regulate iron or repair functions? Biochim. Biophys. Acta 1853, 1513–1527. doi: 10.1016/j. metabolism and symbiotic bacteroid differentiation. Environ. Microbiol. 15, bbamcr.2014.09.018 795–810. doi: 10.1111/j.1462-2920.2012.02835.x Couturier, J., Touraine, B., Briat, J.-F., Gaymard, F., and Rouhier, N. (2013). The Bernard, D. G., Netz, D. J. A., Lagny, T. J., Pierik, A. J., and Balk, J. iron-sulfur cluster assembly machineries in plants: current knowledge and open (2013). Requirements of the cytosolic iron-sulfur cluster assembly pathway in questions. Front. Plant Sci. 4:259. doi: 10.3389/fpls.2013.00259 Arabidopsis. Philos. Trans. R. Soc. Lond. B. Biol. Sci. 368:20120259. doi: 10.1098/ Couturier, J., Wu, H.-C., Dhalleine, T., Pégeot, H., Sudre, D., Gualberto, J. M., et al. rstb.2012.0259 (2014). Monothiol glutaredoxin-BolA interactions: redox control of Arabidopsis Boutigny, S., Saini, A., Baidoo, E. E. K., Yeung, N., Keasling, J. D., and Butland, G. thaliana BolA2 and SufE1. Mol. Plant 7, 187–205. doi: 10.1093/mp/sst156 (2013). Physical and functional interactions of a monothiol glutaredoxin and an Dhalleine, T., Rouhier, N., and Couturier, J. (2014). Putative roles of glutaredoxin- iron sulfur cluster carrier protein with the sulfur-donating radical S-adenosyl- BolA holo-heterodimers in plants. Plant Signal. Behav. 9:e28564. doi: 10.4161/ L-methionine enzyme MiaB. J. Biol. Chem. 288, 14200–14211. doi: 10.1074/jbc. psb.28564 M113.460360 Dlouhy, A. C., Beaudoin, J., Labbé, S., and Outten, C. E. (2017). Brault, A., Mourer, T., and Labbé, S. (2015). Molecular basis of the regulation of Schizosaccharomyces pombe Grx4 regulates the transcriptional repressor iron homeostasis in fission and filamentous yeasts. IUBMB Life 67, 801–815. Php4 via [2Fe-2S] cluster binding. Met. Integr. Biometal Sci. 9, 1096–1105. doi: 10.1002/iub.1441 doi: 10.1039/c7mt00144d Burschel, S., Kreuzer Decovic, D., Nuber, F., Stiller, M., Hofmann, M., Zupok, A., Dlouhy, A. C., Li, H., Albetel, A.-N., Zhang, B., Mapolelo, D. T., Randeniya, S., et al. et al. (2019). Iron-sulfur cluster carrier proteins involved in the assembly of (2016). The Escherichia coli BolA protein IbaG forms a histidine-Ligated [2Fe- Escherichia coli NADH:ubiquinone oxidoreductase (complex I). Mol. Microbiol. 2S]-bridged complex with Grx4. Biochemistry 55, 6869–6879. doi: 10.1021/acs. 111, 31–45. doi: 10.1111/mmi.14137 biochem.6b00812

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Rey et al. Glutaredoxin-BOLA Interactions

Encinar del Dedo, J., Gabrielli, N., Carmona, M., Ayté, J., and Hidalgo, E. (2015). cerevisiae can function as mitochondrial glutaredoxins. J. Biol. Chem. 279, A cascade of iron-containing proteins governs the genetic iron starvation 51923–51930. doi: 10.1074/jbc.M410219200 response to promote iron uptake and inhibit iron storage in fission yeast. PLoS Moseler, A., Aller, I., Wagner, S., Nietzel, T., Przybyla-Toscano, J., Mühlenhoff, U., Genet. 11:e1005106. doi: 10.1371/journal.pgen.1005106 et al. (2015). The mitochondrial monothiol glutaredoxin S15 is essential for Frey, A. G., Palenchar, D. J., Wildemann, J. D., and Philpott, C. C. (2016). A iron-sulfur protein maturation in Arabidopsis thaliana. Proc. Natl. Acad. Sci. glutaredoxin · bola complex serves as an iron-sulfur cluster chaperone for U.S.A. 112, 13735–13740. doi: 10.1073/pnas.1510835112 the cytosolic cluster assembly machinery. J. Biol. Chem. 291, 22344–22356. Mühlenhoff, U., Gerber, J., Richhardt, N., and Lill, R. (2003). Components involved doi: 10.1074/jbc.M116.744946 in assembly and dislocation of iron-sulfur clusters on the scaffold protein Isu1p. Guo, B., Phillips, J. D., Yu, Y., and Leibold, E. A. (1995). Iron regulates the EMBO J. 22, 4815–4825. doi: 10.1093/emboj/cdg446 intracellular degradation of iron regulatory protein 2 by the proteasome. J. Biol. Mühlenhoff, U., Molik, S., Godoy, J. R., Uzarska, M. A., Richter, N., Seubert, Chem. 270, 21645–21651. doi: 10.1074/jbc.270.37.21645 A., et al. (2010). Cytosolic monothiol glutaredoxins function in intracellular Haunhorst, P., Hanschmann, E.-M., Bräutigam, L., Stehling, O., Hoffmann, B., iron sensing and trafficking via their bound iron-sulfur cluster. Cell Metab. 12, Mühlenhoff, U., et al. (2013). Crucial function of vertebrate glutaredoxin 3 373–385. doi: 10.1016/j.cmet.2010.08.001 (PICOT) in iron homeostasis and hemoglobin maturation. Mol. Biol. Cell 24, Nasta, V., Giachetti, A., Ciofi-Baffoni, S., and Banci, L. (2017). Structural insights 1895–1903. doi: 10.1091/mbc.E12-09-0648 into the molecular function of human [2Fe-2S] BOLA1-GRX5 and [2Fe-2S] Iñigo, S., Durand, A. N., Ritter, A., Le Gall, S., Termathe, M., Klassen, R., et al. BOLA3-GRX5 complexes. Biochim. Biophys. Acta 1861, 2119–2131. doi: 10. (2016). Glutaredoxin GRXS17 associates with the cytosolic iron-sulfur cluster 1016/j.bbagen.2017.05.005 assembly pathway. Plant Physiol. 172, 858–873. doi: 10.1104/pp.16.00261 Ojeda, L., Keller, G., Muhlenhoff, U., Rutherford, J. C., Lill, R., and Winge, D. R. Jacques, J.-F., Mercier, A., Brault, A., Mourer, T., and Labbé, S. (2014). Fra2 is a co- (2006). Role of glutaredoxin-3 and glutaredoxin-4 in the iron regulation of the regulator of Fep1 inhibition in response to iron starvation. PLoS One 9:e98959. Aft1 transcriptional activator in Saccharomyces cerevisiae. J. Biol. Chem. 281, doi: 10.1371/journal.pone.0098959 17661–17669. doi: 10.1074/jbc.M602165200 Kim, K.-D., Chung, W.-H., Kim, H.-J., Lee, K.-C., and Roe, J.-H. (2010). Monothiol Outten, C. E., and Albetel, A.-N. (2013). Iron sensing and regulation in glutaredoxin Grx5 interacts with Fe-S scaffold proteins Isa1 and Isa2 and Saccharomyces cerevisiae: ironing out the mechanistic details. Curr. Opin. supports Fe-S assembly and DNA integrity in mitochondria of fission yeast. Microbiol. 16, 662–668. doi: 10.1016/j.mib.2013.07.020 Biochem. Biophys. Res. Commun. 392, 467–472. doi: 10.1016/j.bbrc.2010.01.051 Philpott, C. C., Ryu, M.-S., Frey, A., and Patel, S. (2017). Cytosolic iron chaperones: Knuesting, J., Riondet, C., Maria, C., Kruse, I., Bécuwe, N., König, N., et al. proteins delivering iron cofactors in the cytosol of mammalian cells. J. Biol. (2015). Arabidopsis glutaredoxin S17 and its partner, the nuclear factor Y Chem. 292, 12764–12771. doi: 10.1074/jbc.R117.791962 subunit C11/negative cofactor 2α, contribute to maintenance of the shoot Poor, C. B., Wegner, S. V., Li, H., Dlouhy, A. C., Schuermann, J. P., Sanishvili, apical meristem under long-day photoperiod. Plant Physiol. 167, 1643–1658. R., et al. (2014). Molecular mechanism and structure of the Saccharomyces doi: 10.1104/pp.15.00049 cerevisiae iron regulator Aft2. Proc. Natl. Acad. Sci. U.S.A. 111, 4043–4048. Kumánovics, A., Chen, O. S., Li, L., Bagley, D., Adkins, E. M., Lin, H., et al. doi: 10.1073/pnas.1318869111 (2008). Identification of FRA1 and FRA2 as genes involved in regulating Przybyla-Toscano, J., Roret, T., Couturier, J., and Rouhier, N. (2017). “FeS Cluster the yeast iron regulon in response to decreased mitochondrial iron-sulfur Assembly: Role of Monothiol Grxs and Nfu Proteins,” in Encyclopedia of cluster synthesis. J. Biol. Chem. 283, 10276–10286. doi: 10.1074/jbc.M80116 Inorganic and Bioinorganic Chemistry, eds R. A Scott (New York, NY: American 0200 Cancer Society), 1–19. doi: 10.1002/9781119951438.eibc2470 Lesuisse, E., Knight, S. A. B., Courel, M., Santos, R., Camadro, J.-M., and Dancis, Pujol-Carrion, N., Belli, G., Herrero, E., Nogues, A., and de la Torre-Ruiz, M. A. A. (2005). Genome-wide screen for genes with effects on distinct iron uptake (2006). Glutaredoxins Grx3 and Grx4 regulate nuclear localisation of Aft1 activities in Saccharomyces cerevisiae. Genetics 169, 107–122. doi: 10.1534/ and the oxidative stress response in Saccharomyces cerevisiae. J. Cell Sci. 119, genetics.104.035873 4554–4564. doi: 10.1242/jcs.03229 Li, H., Mapolelo, D. T., Dingra, N. N., Keller, G., Riggs-Gelasco, P. J., Winge, D. R., Qin, L., Wang, M., Zuo, J., Feng, X., Liang, X., Wu, Z., et al. (2015). Cytosolic et al. (2011). Histidine 103 in Fra2 is an iron-sulfur cluster ligand in the [2Fe- bolA plays a repressive role in the tolerance against excess iron and mv-induced 2S] Fra2-Grx3 complex and is required for in vivo iron signaling in yeast. J. Biol. oxidative stress in plants. PLoS One 10:e0124887. doi: 10.1371/journal.pone. Chem. 286, 867–876. doi: 10.1074/jbc.M110.184176 0124887 Li, H., Mapolelo, D. T., Randeniya, S., Johnson, M. K., and Outten, C. E. (2012). Rey, P., Becuwe, N., Tourrette, S., and Rouhier, N. (2017). Involvement of Human glutaredoxin 3 forms [2Fe-2S]-bridged complexes with human BolA2. Arabidopsis glutaredoxin S14 in the maintenance of chlorophyll content. Plant Biochemistry 51, 1687–1696. doi: 10.1021/bi2019089 Cell Environ. 40, 2319–2332. doi: 10.1111/pce.13036 Li, H., and Outten, C. E. (2012). Monothiol CGFS glutaredoxins and BolA- Rietzschel, N., Pierik, A. J., Bill, E., Lill, R., and Mühlenhoff, U. (2015). The basic like proteins: [2Fe-2S] binding partners in iron homeostasis. Biochemistry 51, leucine zipper stress response regulator Yap5 senses high-iron conditions by 4377–4389. doi: 10.1021/bi300393z coordination of [2Fe-2S] clusters. Mol. Cell. Biol. 35, 370–378. doi: 10.1128/ Li, H., Stümpfig, M., Zhang, C., An, X., Stubbe, J., Lill, R., et al. (2017). The MCB.01033-14 diferric-tyrosyl radical cluster of ribonucleotide reductase and cytosolic iron- Rodríguez-Manzaneque, M. T., Tamarit, J., Bellí, G., Ros, J., and Herrero, E. (2002). sulfur clusters have distinct and similar biogenesis requirements. J. Biol. Chem. Grx5 is a mitochondrial glutaredoxin required for the activity of iron/sulfur 292, 11445–11451. doi: 10.1074/jbc.M117.786178 enzymes. Mol. Biol. Cell 13, 1109–1121. doi: 10.1091/mbc.01-10-0517 Lill, R. (2009). Function and biogenesis of iron-sulphur proteins. Nature 460, Roret, T., Tsan, P., Couturier, J., Zhang, B., Johnson, M. K., Rouhier, N., 831–838. doi: 10.1038/nature08301 et al. (2014). Structural and spectroscopic insights into BolA-glutaredoxin Mapolelo, D. T., Zhang, B., Randeniya, S., Albetel, A.-N., Li, H., Couturier, J., complexes. J. Biol. Chem. 289, 24588–24598. doi: 10.1074/jbc.M114.572701 et al. (2013). Monothiol glutaredoxins and A-type proteins: partners in Fe-S Rouault, T. A., and Maio, N. (2017). Biogenesis and functions of mammalian iron- cluster trafficking. Dalton Trans. Camb. Engl. 2003, 3107–3115. doi: 10.1039/ sulfur proteins in the regulation of iron homeostasis and pivotal metabolic c2dt32263c pathways. J. Biol. Chem. 292, 12744–12753. doi: 10.1074/jbc.R117.789537 Melber, A., Na, U., Vashisht, A., Weiler, B. D., Lill, R., Wohlschlegel, J. A., et al. Rouhier, N., Unno, H., Bandyopadhyay, S., Masip, L., Kim, S.-K., Hirasawa, M., (2016). Role of Nfu1 and Bol3 in iron-sulfur cluster transfer to mitochondrial et al. (2007). Functional, structural, and spectroscopic characterization of a clients. eLife 5:e15991. doi: 10.7554/eLife.15991 glutathione-ligated [2Fe-2S] cluster in poplar glutaredoxin C1. Proc. Natl. Acad. Mil-Homens, D., Barahona, S., Moreira, R. N., Silva, I. J., Pinto, S. N., Fialho, Sci. U.S.A. 104, 7379–7384. doi: 10.1073/pnas.0702268104 A. M., et al. (2018). Stress response protein bola influences fitness and promotes Sipos, K., Lange, H., Fekete, Z., Ullmann, P., Lill, R., and Kispal, G. (2002). Salmonella enterica Serovar Typhimurium virulence. Appl. Environ. Microbiol. Maturation of cytosolic iron-sulfur proteins requires glutathione. J. Biol. Chem. 84:e02850-17. doi: 10.1128/AEM.02850-17 277, 26944–26949. doi: 10.1074/jbc.M200677200 Molina, M. M., Bellí, G., de la Torre, M. A., Rodríguez-Manzaneque, M. T., Ströher, E., Grassl, J., Carrie, C., Fenske, R., Whelan, J., and Millar, A. H. and Herrero, E. (2004). Nuclear monothiol glutaredoxins of Saccharomyces (2016). Glutaredoxin S15 is involved in Fe-S cluster transfer in mitochondria

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influencing lipoic acid-dependent enzymes, plant growth, and arsenic tolerance regulatory protein 1. Biochem. Biophys. Res. Commun. 465, 620–624. doi: 10. in Arabidopsis. Plant Physiol. 170, 1284–1299. doi: 10.1104/pp.15.01308 1016/j.bbrc.2015.08.073 Touraine, B., Vignols, F., Przybyla-Toscano, J., Ischebeck, T., Dhalleine, T., Wu, Ye, H., Jeong, S. Y., Ghosh, M. C., Kovtunovych, G., Silvestri, L., Ortillo, H.-C., et al. (2019). Iron-sulfur protein NFU2 is required for branched-chain D., et al. (2010). Glutaredoxin 5 deficiency causes sideroblastic anemia by amino acid synthesis in Arabidopsis roots. J. Exp. Bot. 70, 1875–1889. doi: specifically impairing heme biosynthesis and depleting cytosolic iron in human 10.1093/jxb/erz050 erythroblasts. J. Clin. Invest. 120, 1749–1761. doi: 10.1172/JCI40372 Ueta, R., Fujiwara, N., Iwai, K., and Yamaguchi-Iwai, Y. (2012). Iron-induced Yeung, N., Gold, B., Liu, N. L., Prathapam, R., Sterling, H. J., Willams, E. R., dissociation of the Aft1p transcriptional regulator from target gene promoters et al. (2011). The E. coli monothiol glutaredoxin GrxD forms homodimeric and is an initial event in iron-dependent gene suppression. Mol. Cell. Biol. 32, heterodimeric FeS cluster containing complexes. Biochemistry 50, 8957–8969. 4998–5008. doi: 10.1128/MCB.00726-12 doi: 10.1021/bi2008883 Uzarska, M. A., Dutkiewicz, R., Freibert, S.-A., Lill, R., and Mühlenhoff, U. (2013). Yu, H., Yang, J., Shi, Y., Donelson, J., Thompson, S. M., Sprague, S., et al. The mitochondrial Hsp70 chaperone Ssq1 facilitates Fe/S cluster transfer from (2017). Arabidopsis glutaredoxin S17 contributes to vegetative growth, mineral Isu1 to Grx5 by complex formation. Mol. Biol. Cell 24, 1830–1841. doi: 10.1091/ accumulation, and redox balance during iron deficiency. Front. Plant Sci. mbc.E12-09-0644 8:1045. doi: 10.3389/fpls.2017.01045 Uzarska, M. A., Nasta, V., Weiler, B. D., Spantgar, F., Ciofi-Baffoni, S., Saviello, Zhang, Y., Liu, L., Wu, X., An, X., Stubbe, J., and Huang, M. (2011). Investigation M. R., et al. (2016). Mitochondrial Bol1 and Bol3 function as assembly factors of in vivo diferric tyrosyl radical formation in Saccharomyces cerevisiae Rnr2 for specific iron-sulfur proteins. eLife 5:e16673. doi: 10.7554/eLife.16673 protein: requirement of Rnr4 and contribution of Grx3/4 AND Dre2 proteins. Uzarska, M. A., Przybyla-Toscano, J., Spantgar, F., Zannini, F., Lill, R., Mühlenhoff, J. Biol. Chem. 286, 41499–41509. doi: 10.1074/jbc.M111.294074 U., et al. (2018). Conserved functions of Arabidopsis mitochondrial late-acting maturation factors in the trafficking of iron-sulfur clusters. Biochim. Biophys. Conflict of Interest Statement: The authors declare that the research was Acta Mol. Cell Res. 1865, 1250–1259. doi: 10.1016/j.bbamcr.2018.06.003 conducted in the absence of any commercial or financial relationships that could Willems, P., Wanschers, B. F. J., Esseling, J., Szklarczyk, R., Kudla, U., Duarte, be construed as a potential conflict of interest. I., et al. (2013). BOLA1 is an aerobic protein that prevents mitochondrial morphology changes induced by glutathione depletion. Antioxid. Redox Signal. Copyright © 2019 Rey, Taupin-Broggini, Couturier, Vignols and Rouhier. This is an 18, 129–138. doi: 10.1089/ars.2011.4253 open-access article distributed under the terms of the Creative Commons Attribution Wingert, R. A., Galloway, J. L., Barut, B., Foott, H., Fraenkel, P., Axe, J. L., et al. License (CC BY). The use, distribution or reproduction in other forums is permitted, (2005). Deficiency of glutaredoxin 5 reveals Fe-S clusters are required for provided the original author(s) and the copyright owner(s) are credited and that the vertebrate haem synthesis. Nature 436, 1035–1039. doi: 10.1038/nature03887 original publication in this journal is cited, in accordance with accepted academic Xia, H., Li, B., Zhang, Z., Wang, Q., Qiao, T., and Li, K. (2015). Human practice. No use, distribution or reproduction is permitted which does not comply glutaredoxin 3 can bind and effectively transfer [4Fe-4S] cluster to apo-iron with these terms.

Frontiers in Plant Science| www.frontiersin.org 10 June 2019| Volume 10| Article 712